130 CLIMBING PLANTS. 



One of the strangest things about tendrils is 

 that they do not often clasp each other. Although 

 they are so sensitive to contact, they do not move 

 when rubbed with other tendrils. Darwin says 

 about the Echinocystis : " One of my plants bore 

 two shoots near together, and the tendrils were 

 repeatedly drawn across one another, but it is a 

 singular fact that they did not once catch each 

 other. It would appear as if they had become 

 habituated to contact of this kind, for the pressure 

 thus caused must have been much greater than 

 that caused by a loop of soft thread weighing only 

 the one-sixteenth of a grain." l 



Nor do the tendrils often clasp the stem. When 

 a tendril, revolving horizontally, reaches the part 

 of its course where it would strike the stem of the 

 plant, it rises vertically upward, becomes stiff, and 

 so passes the stem, when it droops to its original 

 position and continues its horizontal course. 



The tendrils of Virginia Creeper (Fig. 37) make 

 little discs, which adhere firmly to the wall or tree 

 on which the vine grows. These discs probably 

 secrete a kind of cement, which glues them firmly 

 to the wall. If the tendrils do not become at- 

 tached to anything, they soon wither and drop 



1 "Climbing Plants/' p. 131. 



